1. Field of the Invention
The present invention is directed to a friction clutch, particularly for a motor vehicle, including a clutch disk which can be coupled in frictional engagement with the crankshaft of an internal combustion engine and which is connected by a hub to a transmission input shaft so as to be fixed with respect to rotation relative to it and can revolve with the latter around a common axis of rotation. The clutch includes an actuation system for producing or canceling the frictional engagement of the clutch disk which is arranged concentric to the transmission input shaft, and a transmission brake for reducing the rotational speed of the transmission input shaft during determined shifting processes of the transmission.
2. Description of the Related Art
U.S. Pat. No. 4,579,203 discloses a friction clutch with a transmission brake in which the actuation system of the friction clutch can execute an additional path following the normal actuation path for the friction clutch in order to activate the transmission brake. The transmission brake includes a brake disk which is arranged on the transmission input shaft so as to be fixed with respect to relative rotation but so as to be axially displaceable and which, in order to carry out its function, can be pressed by the actuation system of the friction clutch against the transmission housing. A construction of this type is disadvantageous due to the fact that the actuation system of the friction clutch must be designed in such a way that it can execute a greater path than is required for the actuation of the friction clutch. This means, for example, that the forces required for actuation of the friction clutch cannot be adapted in an optimal manner to the actuation path. Further, a costly device for wear compensation and for maintaining the constancy of the actuation paths are provided in the prior art.
It is an object of the present invention to provide a friction clutch including a transmission brake which enables an optimal clutch actuation and at the same time actuation of the transmission brake in a predetermined manner.
According to the present invention, this object is met by providing a friction clutch for a motor vehicle, that includes a clutch disk which can be coupled in frictional engagement with a crankshaft of an internal combustion engine. The clutch disk is connected to a transmission input shaft so as to be fixed with respect to rotation relative thereto and can revolve with the transmission input shaft around a common axis of rotation. The friction clutch includes an actuation system for engaging or disengaging the frictional engagement of the clutch disk which is arranged concentric to the transmission input shaft; and a transmission brake for reducing a rotational speed of the transmission input shaft during the shifting of the transmission. The transmission brake is actuated independently from the actuation system. By separating the clutch actuation and the actuation of the transmission brake, it is possible to orient the actuation system to the friction clutch in an optimal manner regardless of the actuation paths of the transmission brake.
According to another advantage of the present invention, all component parts of the transmission brake are integrated in the actuation system of the friction clutch and the friction clutch acts directly on the transmission input shaft. This construction substantially simplifies the handling of the entire actuation system, e.g., during assembly or during disassembly. Further, the direct action of the transmission brake on the transmission input shaft enables an arrangement that is independent from any existing transmission housing.
The actuation of the transmission brake is preferably carried out pneumatically. A pneumatic actuation of the transmission brake is advantageous insofar as there is a high degree of independence with respect to the transmission of the pneumatic medium; further, slight leakiness need not lead to any interference in the actuation system or in the friction clutch.
According to another advantage of the present invention, the actuation system includes a clutch release which is arranged so as to be axially displaceable concentric to the transmission input shaft. The transmission brake can advantageously be integrated in this clutch release.
The clutch release includes a sliding sleeve which carries a clutch release bearing on the side facing the friction clutch. The clutch release bearing communicates with the actuation elements of the friction clutch by its revolving bearing ring. At the same time, a piston is arranged concentrically in the sliding sleeve on the side of the latter facing away from the clutch release bearing. Due to this construction, the sliding sleeve is provided on one of its axial sides with the clutch release bearing and on the other axial side with the piston, so that the two elements are spatially separated from one another.
When the transmission brake is actuated, the piston executes a movement away from the friction clutch. Therefore, the transmission brake can be set in operation by means of the preferably pneumatic movement of the piston, independent from the actuation of the friction clutch.
A brake disk is arranged between the piston and the transmission-side end of the sliding sleeve, which brake disk engages in an external toothing of the transmission input shaft with an internal toothing so as to be axially displaceable but fixed with respect to relative rotation. The outer radial portion of the brake disk can be connected to the sliding sleeve in a frictional engagement. Due to this construction, all component parts of the transmission brake are integrated within the actuation system of the friction clutch.
The sliding sleeve further includes a device for preventing rotation relative to a stationary housing part. This rotation preventing device transmits the forces which are generated during the braking process of the transmission input shaft.
A pressure plate and a stop plate are arranged following the piston in the direction of the transmission, and the brake disk can be clamped between the pressure plate and stop plate. The stop plate is held at the sliding sleeve so as to be fixed with respect to rotation relative to it and so as to be fixed axially. Consequently the brake disk can be integrated in the actuation system of the friction clutch on one hand and can be clamped in by its friction surfaces from both sides on the other hand. The stop plate forms a fixed axial stop, while the pressure plate is arranged so as to be axially displaceable and is actuated by the piston.
Preferably, the sliding sleeve is mounted on the transmission input shaft by the revolving bearing ring of the clutch release bearing so as to be axially displaceable. This results in an especially simple construction and is independent from the design of and from the axial distance of a transmission housing.
The sliding sleeve has two projections which extend out approximately radially outward. A clutch release fork which is rotatably mounted at a housing part engages at these two projections for actuating the friction clutch, wherein a means for preventing rotation is provided between the sliding sleeve and clutch release fork. In this way, the clutch release fork which is fastened to a housing part in any case is utilized additionally as a torque support during the actuation of the transmission brake.
Other objects, advantages, and features of the present invention will be apparent from the following detailed description of a specific embodiment thereof when read in conjunction with the accompanying drawings.